Electrtical heating device



ELECTRICAL HEATING DEVICE Filed Feb. 1, 1923 V [WA avian fLwigflbk Patented July 19, 1927.

.' UNITED STATES nnwnv L. winoaivn,

0F DORMONT BOROUGH, PENNSYLVANIA.

ELECTRICAL HEATING DEVICE.

Application filed February 1, 1923. Serial m.61e,445.

This invention relates to improvements in electrical heating units of the conduction type wherein the resistor element is entirely encased or embedded in a mass of suitable material of a monolithic nature that is bound by adhesion within a comparatively shallow depression or recess of a suitable metal base or receptacle into which it ispressed during the process of Illtlllllltltlllll'fi.

in connection with electrical heating units of the foregoing nature, as constructed prior to my present improvements, considerable dilliculty has arisen from thecmbeddmg material cracking, or loosening from the walls and surface of the recess of the base, due to the dilierence in the respective coetlicicnts of expansion of the base and embedding material, or to shrinkageof-the embedding material while being tired, or from use at high temperature. There is no way of always entirely overcoming these inherent difl'erences, so that the solution of the problem lies in so constructing the unit that any relative change in extent of the two constituents is compensated for or nulliiied, or made ineffective as a cause of deterioration.

To this end-:fmy invention has for its object to produce an electrical heating unit of the character setforth wherein the depression or recess of the base is divided into a plurality of relatively small communicating cells-preferably as many as is consistent with commercial practice-as by means of ribs or walls, each cell being defined or enclosed by not less than three ribsor walls arranged at an angle to each other. This has the efi'ectof breaking up the mass of embedding material into many comparatively small connected parts or sections and avoids the large uninterrupted expanse that is present in the earlier constructions. By so apportioning the mass of embedding material into small parts or sections, the rela- 2 tion between each part or section and the surrounding metal parts is so changed as to minimize and render practically null the effects resulting from the dillerence in the expansion or contraction of the two main constituents of the unit.

Advantages arising from this improved construction, aside from that of eliminating cracking and loosening of the embedding material, are: Protection of the resistor and its insulating sheath against mechanical in jury, enhanced mechanical strength, due to the source of heat,

and

service,

the presence of theribs; 9. minimum thickness and weight of the metal base or receptacle; increased efficiency through quicker and more uniform distribution of heat and a more rapid temperature rise with a given rate of energy input; increased facilities for the abstraction of heatenergy from the resistor resulting in operation at a lower resistor temperature, prolonging life of same; economy of operation; and the promotion and maintenance during the process of manufuctui'e and the life of the device, of me; chanical and thermal unity, that is, an absolute continuity of heat conducting substance between the resistor element, which is and the heat yielding surface of the unit, which is so essential to the effectiveness and durability of a conduction type heating unit.

Broadly, then, the aim of my invention is the production of a highly eflicient, substantial and durable electrical heating unit of the embedded type for incorporation in.

hot plates, stoves and ranges, melting pots, in other electrically heated up liances, and which will readilywithstand the hard severe strains and the abuses to which appliances of this character are ordinarily subjected.

An embodiment of the invention is illustrated in the accompanying drawing wherein Fig. 1 is a bottom plan View of an electrical heating unit designed for use in hot plates, stoves, ranges or the like' and Fig. 2'is a section on the line 2-2 of ig. 1.

Describing the invention by the use of reference numerals, 1 designates the base or receptacle which is flat and smooth on one side, to provide a suitable heating surface or working face, while on the formed with a comparatively shallow recess that is enclosed by a peripheral flange 2. Extending radiall opposite sides of the as ends,spaced rom part of the recess eninwardly from the flange to a po nt slig tly beyond the center of 1 as in radial alignment other side it is 5, are ribs 6, the ones 1 4 is not a complete.

heads 13 encased closed by the flange 4 communicates with that section between flanges 4 and 5. There is no communication, however, between the sections of the recess that are, separated by the flange 5.

The recess contains, to the'depth shown in Fi 2, a suitable embedding material 10 which has been pressed tirnily within the recess during the process of manufaetm-e. Binding posts or terminals, designated It and 12, have their enlarged inner ends or within the embedding material enclosed by the flange 4 and a resistor element-14, preferably in the nature of a flat wire or ribbon of suitable metal. has one of its ends connected to the terminal it and is led therefrom through the opening between the adjacent end of the flange-4 and the wall 3 and throughout a tortuous course between the flanges 4 and 5 and among the ribs 6 to where it is led in through the space between the opposite end of the flange 4 and the wall 3 to the binding post 12, the resistor element being given a serpentine formation so that it will extend into all corners and be properly distributed throughout the entire aunt of that section of the recess located inwardly of the flange 5.

Binding posts or terminals 15 and 16 are disposed on opposite sidw of that section of the wall 3 which extends between the flanges "2 and '5, anda resistor element 17 of se pentine formation is led from one to t e I other thereof, throughout the space between the flanges'2 and 5, and'ainong the ribs 6 which sub-divide such space, in the manner shown. 7

When the-unit is. properly connected, through a circuit containing a suitable switch, with a sourceof electric cner the entire unit may be rendered operative by energizing both resistor elements 14 and 17; or, by cuttin out one or the other or by throwing bot in series, the heat may be reduced, the inner element 14 eflecting a greater and more concentrated heat than the element 17. Consequently, three heats may be realized through the use of the unit.

Now that the invention has been specifically described, its purpose may be more fully appreciated if brief consideration is given to the situation which led to its conception.

Prior to my invention, as has already been pointed out, diflicult-y was experienced in eflecting a proper bond between the elec trical insulating heat conducting material in which the resistor is embedded and .the surface of the base contacts. Due to wherewith said material the difference in coefficients of expansion of the metal whereof the base is formed and of the embedding material, and notwithstanding the very high ressure employed in compressing the materia with in the recess or cavity, the embedding material that serve to mechanically secure would break away from the surface of the. base throughout enlarged areas and in some cases would shrink away from the peripheral walls of the recess, thus becoming loos-- ened, and it' it. would not entirely fall away it would create a gap between the. mass of embedding material and the luise. which would greatly impair the life of the unit and materially reduce its thermal etliciency, the latter being the obvious result of the separation between the material and the base.

Through my present invention the foregoing dilliculties are entirely overcome and intimate and permanent contact of the embedding niatcrial with the base is eti'ected. Two factors contribute to this result: First, the dividing ot' the embedding material into relatively small sections so that the efl'eet resulting fronrtlie dillereiice in coellicients of expansion of the two substances is miniiiiized and therefore of no practical consequence: and second. the. binding of the material to the base through the flanges and ribs which are in effect anchorage elements the embedding material to the body portion of the base.

Having thus described my invention, what I claim is:

1. An electrical heating unit of the character set forth comprising a base havin an annular flange enclosing a recess, a we extending from said flange radially inwardly to substantially the center of the recess, a second annular flange substantiallv concentric with the former flange, the second flange being iiiterru ted in its circumference and havin its en s need on opposite sides of the a oresaid wal ribs extending inwardly from the first mentioned flange, other ribs extending outwardly from the second flange in staggered relation to the former ribs, 9. body of embedding material occupyi the recess, terminals embedded within sai material and disposed on opposite sides of the said wall within the space enclosed by the second flange, and a resistor element of serpentine formation extending from one of the terminals throu h the space between one endof the second ange and the said wall and in a tortuous course throughout the space between the first and second flanges and among the aforesaid ribs and through the space between the other end of said secon flange and said wall to the other terminal.

2. An electrical heating unit of the character set forth comprising a base having a continuous flange enclosin a recess, a second continuous flange spaced inwardly from the first flange and dividing the recess into an outer portion and an inner portion, a third flange spaced inwardly from the second flange, the third flange being non-continuous and having its ends spaced apart,

also

v and subdividing the recess, a body of em;

ribs extending from certain of said flanges bedding material occupying each portion of the recess, a pair of terminals embedded Within the material occupying the outer portion of the recess, a resistor element of serpentine shape extending from one of the terminals throughout the outer portion of the recess to the other terminal, a pair of terminals situated within the space enclosed by the third. flange, and a resistor element.extending from one of the last ment oned terminals throughout the space between the second and third flanges to the other of the last mentioned terminals.

3. An electrical heating unitvof the character set forth comprising a base having an annular peripheral flange enclosing a recess, a wall extending radially inwardly from said flange toward the center of the recess, a second annular flange spaced inwardly from the peripheral flange and sub stantially concentric therewith and dividing the recess into an annular outer portion and a 'circular inner portion, a third annular flange spaced inwardly from the second flange and concentric therewith, the third flange being interrupted in its circumference and having its ends spaced in opposite directions from said radial wall, ribs extending inwardly from the peripheral flange, ribs extending outwardly from the third flange, and ribs extending inwardly and outwardly from the second flange thereby to divide the annular and circular portions of the recess into a pluralitv of cells, a body of embedding material occupying each portion of the recess, a pair of terminals embedded within the material occupying the outer portion of the recess and situated one on each side of and adjacent to the radial wall, a resistor element of serpentine shape extending from one of the terminals in a tortuous course throughout the outer portion of the recess to the other terminal, a pair of terminals situated one on each side of the radial wall within the space enclosed by the third flange, and a resistor element extending from one of said terminals through the space between the second and third flanges to the other termi a1.

In testimony whereof, I hereunto aflix my signature.

'EDWIN L. WIEGAND. 

